Polymer films have a tendency to cling to each other so that in further processing film layers can often only be separated from each other with very great difficulty. The underlying mechanisms of that ‘blocking’ are not completely understood, but inter alia the following aspects of adhesion forces are referred to in the literature:                process parameters, for example temperature and pressure,        migration of low-molecular polymer constituents,        electrostatic and other attractive forces, and        surface structure.        
Minimisation of the necessary force for the separation of film layers is dependent on the above-mentioned aspects and the influence on the reduction in the adhesion forces is defined as ‘anti-blocking’.
In the production of polymer films, usually organic or inorganic additives such as fatty acid compounds or inorganic particulate material predominantly silicate-based are used in the state of the art for that purpose, which induce surface roughness and which thus function as a ‘spacer’ between the film layers, whereby the adhesion forces are minimised. By way of example attention is directed here to G Wypych ‘Handbook of Antiblocking, Release, and Slip Additives’ (Hanser Verlag—2005) or H Zweifel, ‘Plastics Additives Handbook’ (Hanser Verlag—2000) as well as WO 96/001289.
On the other hand those organic or inorganic additives, besides that desired effect of the COF reduction (coefficient of friction) at the same time also exert an unwanted adverse influence on the optical properties such as for example gloss, haze, transmittance and processibility of the polymer so that it is often necessary to arrive at a compromise between process-engineering and optical demands on the film.
An additive which satisfies those aspects in many respects is however not known in the state of the art and therefore the object of the invention was to provide an additive which can both be well incorporated into the polymer and which also allows the polymer compounded with the additive in that way itself to be well processed and which imparts to the polymer good optical properties with at the same time outstanding ‘anti-blocking’ properties.
On the part of the inventors it has now surprisingly been found that such an additive can be obtained by means of the process having the features set forth in the main claim.